Nice article, and I'm glad someone is taking a serious look at the problem. I have an idea, and some additional analysis.

The idea: Use a physical key, and send a duplicate key ahead via FedEx or some other delivery service rather than trying to travel with a key. That won't protect you if you've been specifically targeted by the authorities (since the key could be intercepted enroute), but it will frustrate fishing expeditions.

The analysis: In many developed countries, the threat is unique to the short time after you've physically crossed the border but before you've cleared customs. Once you clear customs, if the authorities want to compel access to your laptop, they need a warrant or some other specific legal authority (under normal circumstances--I'm considering the case of a businessperson or lawyer who has sensitive documents, not the case of someone who might attract scrutiny from agencies more accustomed to operating outside the law). So for many travelers, a sufficient level of protection needs only to deflect the customs agent's attention enough to get cleared. Customs can't go back and demand access once a traveler has passed into the country (in many countries).

The catch is that any obvious protection or encryption will, in itself, attract the attention of customs, and in some backward places (like the United States), Customs can detain you indefinitely until they're satisfied you've handed over all the goods. Any scheme which is visible to a customs agent is likely to cause great problems to the traveler: it's like trying to clear customs while carrying a welded-shut steel box. They will be intensely curious as to the contents of the box, and don't expect to go anywhere until someone fires up a cutting torch.

So what you really need is a combination of encryption plus the electronic equivalent of a cloaking device.

Ideally, the computer should function perfectly normally if booted or accessed without the special key, but sensitive files simply won't appear in the filesystem. Unless customs is specifically targeting you, this should get you safely through (and even if they make you leave a disk image behind, the encryption should protect the secrets against a more detailed analysis).